Words and designs are frequently printed onto clothing and other textile materials, and other objects. The use of computer technology allows substantially instantaneous printing of images. For example, video cameras or scanning may be used to capture an image to a computer. The image may then be printed by any suitable printing means, including mechanical thermal printers, ink jet printers and laser printers. These printers will print multiple color images.
Color ink jet printers are in common use. Color ink jet printers use combinations of cyan, yellow and magenta inks or dyes to produce multiple color images. Most ink jet printers in common use employ inks which are in liquid form.
Heat activated, dye diffusion and sublimation ink solids change to a gas at about 400.degree. F., and have a high affinity for polyester and other synthetic materials at the activation temperature, and a limited affinity for most other materials. Once the bonding from gassification and condensation takes place, the ink is permanently printed, and is resistant to change or fading caused by laundry products, heat or light.
Hale, U.S. Pat. Nos. 5,246,518, 5,248,363, 5,302,223, and 5,485,614 and Hale et al., U.S. Pat. No. 5,488,907, disclose the use of printers to produce an image on a medium or transfer sheet wherein the image is comprised of sublimation, dye diffusion or other heat activated inks. The ink is not activated during the printing of the medium or transfer sheet.
Problems are associated with liquid inks prepared from insoluble dye solids. The orifices or nozzles of most ink jet printers are not designed for the dispensing of dye solids contained within a liquid material. The orifices of these printers are typically 5-30 microns in diameter, and clogging of the orifice will occur when ink solids of large particle size or in high volume are transferred through the orifice.
Further, when the ink solids are placed into a liquid carrier, the ink solids tend to separate from the liquid over time and fall to the bottom of the ink container. The ink is typically packaged in a container at a manufacturing facility for subsequent mounting of the container within the ink jet printer, meaning that a substantial storage time for the ink composition exists prior to use. Separation of the liquid and solids comprising the ink formulation presents problems with regard to the mechanical operation of the printer and the print quality achieved from use of the ink formulation. Agents which are included within the ink formulation to inhibit separation must also inhibit agglomeration of the solid dye particles, but the agents must not inhibit activation of the dye during the final transfer at elevated temperatures, by insulating the dye or reacting with the dye, or otherwise.
Accordingly, the production of stable liquid inks from dyes which are not water soluble is difficult to achieve without destroying or reducing the properties of the dye which are required for practicing the process of the invention. In the prior art, liquid inks have been produced from dyes that initially have properties suitable for practicing the process. However, the production of liquid inks from these dyes changes or masks the required properties, and therefore, the resulting inks cannot be satisfactorily used to practice the process. For example, additives which will inhibit the dye particles from settling out of the liquid carrier, or which will inhibit agglomeration, tend to insulate the dye particles, meaning that the energy required for sublimation, diffusion or activation of the dye is elevated to unacceptable levels for practicing the process. Other additives which are used in the prior art to produce a liquid ink from the solid dyes are reactive with the dye, and modify or eliminate required properties of the dyes. Other "side effects" of using these additives include undesired color modification or contamination, bonding with the intermediate substrate, or optical density on the final substrate which is inadequate.
While certain solvents will dissolve the dyes, the requirements of the process makes the use of these solvents impractical. Dye materials solubilized to the molecular level have a tendency to bond with fibers, both synthetic and natural. Accordingly, the dyes cannot be effectively transferred from a substrate used as an intermediate transfer sheet by the application of heat and pressure as required by the process of the present invention.